Approaches for Establishing Predicted-No-Effect Concentrations for Population-Level Ecological Risk Assessment in the Context of Chemical Substances Management

Abstract

The establishment of rational frameworks for population-level ecological risk assessment (PLERA) in the context of chemical substances management is an important issue. We illustrate two feasible approaches for establishing predicted-no-effect concentrations (PNECs)for PLERA through a case study of 4-nonylphenol (4-NP) using life-cycle toxicity data for medaka (Oryzias latipes). We first quantified the potential impacts of 4-NP on medaka in terms of reduction of population growth rate (i). An age-classified population matrix model (daily time-step) was developed and used to combine life-cycle survivorship and fecundity data obtained from individual-level responses of medaka expDsed to 4-NP into population-level responses defined by the parameter lambda. Thereafter, from the resulting lambdas, two approaches for establishing population-level PNEC values were proposed and examined. We then derived the PNEC values for population-level impacts, based on (a) the threshold concentration, defined as the chemical concentration at which lambda = 1 as a value with a 95% confidence interval, and (b) the no-observed-effect concentration (NOEC) and the maximum-acceptable-toxic concentration (MATC). The results suggest that PNEC values of 4-NP ranging between 0.82 and 2.10 microg/L affect medaka population growth. Although these approaches have their limitations, current knowledge indicates that they are reasonable and practical for evaluating population-level impacts of chemicals, thereby serving as a case study for establishing PNEC values for PLERA in the context of chemical substances management and decision-making.

Making leaps in amphibian ecotoxicology: translating individual‐level effects of contaminants to population viability

“…For example, many studies evaluating the detrimental effects of environmental contaminants have relied on standard toxicological methods that measure effects on individual organisms (Cairns and Pratt 1993, Clements and Kiffney 1994, Stark 2005. Long-standing recognition of the limitations of this approach (Cairns 1984, Kimball and Levin 1985 prompted several studies that used integrative methods to bridge the gap between individual-level effects of environmental contaminants and population-level processes (e.g., Forbes and Calow 2002, Tanaka 2003, Miller and Ankley 2004, Lin et al 2005, but this approach has seldom been applied to terrestrial vertebrates (but see Nakamaru et al 2002, 2003, Karraker et al 2008, Salice et al 2011.…”

Population‐level ecological effect assessment: estimating the effect of toxic chemicals on density‐dependent populations

“…To promote population-level ecological risk management, the development of methods to estimate population-level effects of chemicals from individual-level laboratory toxicity test data are needed by risk assessors and managers. Previous studies of population-level ecological risk assessment have mainly employed intrinsic growth rate as an index of population-level effects (e.g., Forbes and Calow 2002;Forbes et al 2001a;Hendriks and Enserink 1996;Kuhn et al 2000;Lin et al 2005;Naito and Murata 2006;Raimondo et al 2006;Stark et al 2004). To estimate the effects of chemicals on intrinsic growth rates, mathematical models of population dynamics (e.g., logistic growth model, Leslie life-stage model) combined with knowledge of the relationship between a chemical's concentration and its effects on individual traits (e.g., individual survivability and fertility; hereafter, we consider toxic effects on these vital rates as individual-level effects) determined by laboratory tests have often been used (e.g., Lin et al 2005;Naito and Murata 2006;Raimondo et al 2006).…”

Development of aquatic life criteria in China: viewpoint on the challenge

“…Nevertheless, biomarkers such as vitellogenin, secondary sexual characteristics, gonadal somatic index, concentrations of steroids in blood plasma, and gonadal histology are considered "signposts" in the environmental risk assessment of endocrinedisrupting chemicals (EDs) (Hutchinson et al 2006), and detection of such signposts determines priority for the chemical and biological analysis for water, sediment, and biota. The potential to use biomarkers as signposts was evaluated by determining the occurrence of false negatives and false positives (Hartung 2009;Bosker et al 2010) and it has been suggested (Lin et al 2005) that effects at the molecular or hormonal level will not necessarily be transmitted to higher level ecological effects because of the innate ability of organisms to repair damage or adapt physiologically to the effects (damage) caused by stressors. By contrast, if a population is affected by toxicity of a chemical, then the functions and structures of the ecosystem could also be affected (Lin et al 2005).…”

“…The potential to use biomarkers as signposts was evaluated by determining the occurrence of false negatives and false positives (Hartung 2009;Bosker et al 2010) and it has been suggested (Lin et al 2005) that effects at the molecular or hormonal level will not necessarily be transmitted to higher level ecological effects because of the innate ability of organisms to repair damage or adapt physiologically to the effects (damage) caused by stressors. By contrast, if a population is affected by toxicity of a chemical, then the functions and structures of the ecosystem could also be affected (Lin et al 2005). Maintaining the viability of populations of plants and animals is a key focus of environmental regulation.…”